Using OS 10.12.4 and Photos 2.0 (3150.4.120).
I imported a bunch of photos recently, and selected View > Sort > "Keep Sorted by Oldest First".
Most of them appear in the correct order, but a few are out of order. If I do Get Info on them, I can see that certain photos have a later date than photos appearing later in the album.
Is this sort order based on a different date? How can I make them appear in the right order? Or is this just a bug in Photos (in which case I'll abandon hope)?
It also uses this same incorrect order on iOS 10.3.1, when I sync them to my iPhone.
I tried putting them in a new album, as well as creating a Smart Album with the photos, but the same order persists.